Tube assembly with a breakaway plug

ABSTRACT

An assembly of a tube having a breakaway plug mounted on one opening thereof is provided. The plug includes a hollow cylindrical segment fixedly secured to the tube, a closing segment, and a frangible annular portion located in the hollow segment apart from the secured portion. The plug is formed of material having a Shore A hardness of 68-76 such that the plug can be torn off at the frangible portion by twisting. Since the plug of relatively flexible material having a Shore A hardness of 68 to 76 is attached to the tubular body, the gas tightness and intimate contact therebetween are substantially improved to minimize the risk of the plug being accidentally ruptured by an external force when the tubular body is not on use, while maintaining the ability of breakage of the plug when the tubular body is on use. 
     Preferably, there is provided a protector with such a hardness that it may not prevent breakage of the plug at the frangible portion for safeguard and easy breakage of the plug.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a tube assembly with a breakaway plug. Moreparticularly, it relates to a tube assembly having a breakaway plugwhich is unlikely to be ruptured or contaminated before use.

2. Discussion of Prior Art

In some branch tubes such as four-way branch tubes for use incombination with blood collection bags, all the branches are not used atthe same time, but they are used one by one in successive steps. Toprevent the flow path from being contaminated from a branch which is notin use, the branch not in use should be completely sealed with a plug ora suitable closure. Upon use of the branch which has been sealed with aplug, it is necessary that the plug be readily broken and removed toopen the associated branch to allow for connection to another membersuch as a tube having a puncture needle.

A variety of plugs which can be torn off have been proposed in the priorart. For example, T. Gewecke, U.S. Pat. No. 3,368,560 discloses anoutlet fitting wherein a cap portion is united to a tubular portion bymeans of a relatively thin annular web. A finger tab depending from thecap portion is pulled whereupon a line of severance occurs in the areaof the integral web.

This fitting is applicable as a plug on a branch of a four-way branchtube, but has a problem in operation. When the cap is pulled with aconsiderable force in an axial direction to cut the cap at the thin web,there occurs an impact of reaction At the instant of rupture, theoperator would probably hit something at her elbow. Additionally, thecut edge would be brought in contact with something so that it might becontaminated.

C. Robinson et al, U.S. Pat. No. 4,228,835 discloses a breakaway capcomprising a ring having an open end and a closed end with a handle Anannular grooved area is provided as a frangible connection between theopen end portion and the closed end of the ring. When the handle isgrasped and moved angularly, the ring will break at the frangiblesection to remove the handle from the ring. The cap is formed of apolyvinyl chloride having a hardness in the range of 85-100 as measuredon the Shore A scale of a durometer.

This cap is also applicable as a plug on a branch of a four-way branchtube and considered as preventing the inadvertent reaction of breakageinevitable with the cap of Gewecke. The cap has a certain degree ofhardness so that it is broken at the frangible section by moving thehandle angularly. Since the plug or breakaway cap is united with thefrangible section and a flexible tube is connected to the ring portionof the cap left after breakage, the ring portion of the cap must beutilized as a waist in bending the handle. For this reason, the cap ismade of a material having a Shore A hardness of 85-100. Since the cap ofthis range of hardness is rather less flexible, it has problems in gastightness, adherence to the branch or tubular body, and prevention ofaccidental rupture before it is desired to break the plug to open theflow path of the branch on use.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a tube assembly havinga breakaway plug which is mounted on a tubular body in an air-tight andintimate contact manner without the risk of being accidentally rupturedor contaminated during manufacture or transportation, but can be readilytorn off upon use.

According to the present invention, there is provided a tube assemblycomprising

a tubular body of a relatively rigid material having at least two openends, and

a plug of a material having a Shore A hardness of from 68 to 76 mountedon one open end of the tubular body, the plug including (a) a hollowmount segment having an open end, a portion of the mount segmentextending from its open end being fixedly secured to the one open end ofthe tubular body, (b) a closing segment axially connected to the mountsegment, and (c) a frangible portion located axially outside the securedportion whereby the plug is breakable at the frangible portion andremovable from the one open end of the tubular body.

Preferably, there is provided a protector with such a hardness that itmay not prevent breakage of the plug at the frangible portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the inventionwill be better understood by reading the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a partially cross-sectional plane view of a four-way branchtube with a breakaway plug according to one embodiment of the presentinvention;

FIG. 2a is an exploded cross-sectional view of the tube assembly of thepresent invention showing a tube branch, a plug and a protector in adisassembled state;

FIG. 2b is a cross-sectional view of the tube assembly showing a tubebranch, a plug and a protector in an assembled state;

FIG. 3a and 3b are cross-sectional views of the plug taken along linesA--A and B--B in FIG. 2a, respectively;

FIG. 4a and 4b illustrate a plasmapheresis system having the tubeassembly of the invention incorporated therein; and

FIG. 5 is a cross-sectional view of a four-way branch tube with abreakaway plug according to another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The tube assembly of the present invention includes a tube body havingat least two open ends. Any tubular body having at least two open endsbetween which a flow path extends may be employed. Although a commonlyused four-way branch tube is referred to as a typical example in thefollowing description, the present invention is not limited to thefour-way branch tube. Among various medical tubes, four-way branch tubesare widely used in combination with blood collection bags.

FIG. 1 illustrates a four-way branch tube as one embodiment of the tubeassembly of the present invention. The four-way branch tube with abreakaway plug generally designated at A includes a tubular body 1having four openings, a plug 2 mounted on one opening of the tubularbody 1, and a protector 3 fitted over the plug for protecting the plug.The tubular body 1 has one main tube and two branches connected theretoat an angle in a usual manner. The tubular body 1 has four openings, afirst opening 4, a second opening 5, a third opening 6, and a fourthopening 7. For brevity of description, the first opening 4 is designateda proximal side, and the second, third and fourth openings 5, 6 and 7are designated distal sides because the first opening 4 is connected toa blood collecting needle as shown in FIG. 4a. The distal end of themain tube or the third opening 6 is provided with a closure member 8which normally closes the flow path, but is breakable to open the flowpath. The feature of the present invention resides in the second branchdefining the fourth opening 7 on which the plug 2 and the protector 3are mounted.

The components are described in detail in FIG. 3a, which is across-sectional view of the branch defining the fourth opening 7, theplug 2, and the protector 3 in an exploded state. A full assembly ofthese components is shown in FIG. 3b. The branch of the four-way branchtube has a flow path-defining bore 7 terminating at an open end andincludes a distal wall portion 9 having a smaller outside diameter thanthe remaining. A step 10 is formed between the distal wall portion 9 andthe remaining. The outside wall of the branch is stepped to form thesmaller outside diameter wall portion 9 for mounting the plug 2 thereon.The bore 7 of the branch is Luer tapered at 7a.

The tubular body 1 is formed of a relatively rigid material such aspolycarbonate. Since the breakable closure member 8 is integrally formedwith the tubular body within the third opening 6, formation of thetubular body and the closure member from a rigid material makes it easyto tear off the closure member. The use of a rigid material is alsouseful to connect a male Luer connector to the branch from which theplug 2 has been torn off for cell return purpose. If the tubular bodywere formed of a flexible material other than polycarbonate, it would bedeformed during autoclave sterilization so that the Luer taper 7a mightdiminish.

The plug 2 includes a hollow mount segment providing an open end 11 atone end and a closing segment axially connected to the mount segment andproviding a closing end 12 at another end. The hollow mount segmentincludes a first wall portion 13 with a relatively smaller innerdiameter extending from the open end 11 and a second wall portion 14with a relatively larger inner diameter extending from the first wallportion 13 to the closing segment. The first wall portion 13 is fixedlysecured to the distal wall portion 9 of the branch defining the bore 7as shown in FIG. 2b. The closing segment may be either a solid segment(not shown) or a hollow segment as shown in FIG. 2a as long as itprovides a closing end to the bore of the hollow mount segment. The sumof axial length of the first and second wall portions 13 and 14 of theplug 2 is at least equal to, preferably greater than the axial length ofthe distal wall portion 9 of the branch defining the bore 7 to ensurefirm attachment between the branch and the plug and allow easy tearingof the plug at a frangible portion.

The plug 2 is provided with a frangible portion in the form of acircumferential notch 15 in the outer surface whereby the plug isbreakable at the frangible portion and removable from the tubular bodyor branch. The frangible portion 15 is located such that when the plug 2is engaged and secured to the distal wall portion 13 of the branchdefining the fourth opening 7, the frangible portion is spaced apartfrom the secured portion. Namely, the frangible portion 15 is located inthe second wall portion 14 having a larger inner diameter. In otherwords, the distal wall portion 9 of the branch axially extends beyondthe frangible portion 15 of the plug 2 toward the closing segment. Thenthe open end of the distal wall portion 9 of the branch is exposed whenthe plug 2 is torn off. It is then very easy to connect another memberhaving a needle to the protruding open end 9 of the branch. Theprotruding end of the branch minimizes the possibility of the othermember contacting the cut edge of the plug kept attached on the distalwall portion 9 which might be contaminated, avoiding contamination ofthe flow path of the tubular body 1.

According to the present invention, the material of which the plug 2 ismade has a Shore A hardness in the range between 68 and 76, preferablybetween 74 and 76. Shore A hardness used herein is one scale ofdurometer hardness applied to represent the hardness of relativelyflexible plastics as prescribed by the American National Standard, ASTMD2240-75.

As previously described, the tubular body 1 is made of a relativelyrigid material such as polycarbonate. Then the portion of the plug 2which is attached to the hard tubular body 1 serves as a support so thata tearing force applied to the plug by fingers does not disperse, butconcentrates at the frangible portion 15 to facilitate breakage thereof.Nevertheless, an external force other than the carefully applied foldingforce by fingers is absorbed by the plug 2 which itself is of flexiblematerial and not directly applied to the frangible portion, minimizingthe risk of the plug being accidentally broken at the frangible portion.

The plug 2 having a Shore A hardness of less than 68 is too soft so thatit can be bent, but is difficult to break.

Experimental data are shown below. Test pieces having the same structureas the plug disclosed in U.S. Pat. No. 3,368,560 were prepared frommaterials having varying hardness and measured for tensile strength andflexural strength at rupture. The results are shown in Table 1. Tensilestrength and flexural strength were measured at a pulling rate of 10mm/min. and 20 mm/min. and reported as an average of ten and fivemeasurements, respectively.

                  TABLE 1                                                         ______________________________________                                        Sample                                                                              Shore A     Tensile strength                                                                          Flexural strength                               ______________________________________                                        1     64-68       3.9 kg      unmeasurable                                    2     68-70       4.0 kg      unmeasurable                                    3     74-76       4.9 kg      unmeasurable                                    4     90-92       9.7 kg      2.5 kg                                          5      98-100     16.4 kg     6.8 kg                                          ______________________________________                                    

It is seen from Table 1 that those test pieces of material having aShore A hardness of from 64 to 76 cannot be ruptured by bending.

Test pieces of the plug according to the present invention as shown inFIG. 2a were prepared from materials having varying hardness andmeasured for tensile strength and flexural strength at rupture. Theresults are shown in Table 2. Tensile strength and flexural strengthwere measured at a pulling rate of 20 mm/min. and 50 mm/min. andreported as an average of ten and five measurements, respectively.

                  TABLE 2                                                         ______________________________________                                        Sample                                                                              Shore A     Tensile strength                                                                          Flexural strength                               ______________________________________                                        6     68-70       4.7 kg      3.9 kg                                          7     74-76       7.0 kg      3.8 kg                                          8     87-92       10.2 kg     5.7 kg                                          ______________________________________                                    

It is seen from Table 2 that plugs having a Shore A hardness of 68 to 76can be more easily ruptured by bending than plugs having a Shore Ahardness of 87 to 92.

The plug preferably has a cross sectional shape other than a circle on adistal side with respect to the frangible portion 15. FIGS. 2a and 2bare cross sections taken along lines A--A and B--B in FIG. 3a,respectively. More particularly, the first wall portion 13 of the plug 2with a relatively smaller inner diameter which is to be secured to thedistal wall portion 9 of the branch defining the bore 7 hassubstantially a true circular cross section, as shown in FIG. 3a havingan inner diameter substantially equal to the outer diameter of thedistal wall portion 9. The remaining portion of the plug 2, preferablythe closing segment has a non-circular cross section in a directiontransverse to an axial direction. For example, the closing segment has asquare cross section as shown in FIG. 2b. Since the closing segment is adistal segment of the plug which not only closes the bore in the hollowmount segment, but also serves as a handle or lever upon breaking theplug at the frangible portion, the closing segment may have arectangular, ellipsoidal or other cross section which is convenient tomanually grip.

The tube assembly of the present invention also includes the protector 3to be fitted over the plug 2. The protector 3 is in close fit with theoutside of the plug 2 for protecting the plug. In the example of FIGS.2a and 2b the protector 3 is a grip which defines therein a cavityhaving an open end and a closed end. An inside portion of the cavitymates with the closing segment of the plug 2. The shape of the protector3 is not limited to that shown in FIG. 3a and the protector may be atubular sleeve having a portion to be tightly engaged over the closingsegment of the plug 2.

In order that the plug 2 be readily torn off by grasping and twistingthe protector 3, the protector 3 preferably has a non-circular outerconfiguration such as a rectangular, square and ellipsoidal crosssection in a direction transverse to an axial direction.

FIG. 2b shows the components in an assembled state. The plug 2 ismounted on the branch to close its opening 7 and also covered with theprotector 3. The first wall portion 13 of the plug is in snug fit overthe distal wall portion 9 of the branch. A space 16 is left between thesecond wall portion 14 of the plug and the distal wall portion 9 of thebranch in a radial direction. The space 16 is sufficient to keep theopen end of the branch 4 from obstructing in breaking of the plug 2 atthe frangible portion 15. For the same reason, the distal or open end ofthe branch 7 is axially spaced apart from the plug 2.

The protector 3 must be in snug fit over the plug 2 in order to protectthe plug 2 from any accidental external force and to prevent any slidingmotion between the protector and the plug when the protector 3 istwisted with a finger grip to tear off the plug 2. The protector is inclose fit on the closing segment of the plug 2, but axially extends overthe frangible portion 15 with a spacing from the mount segment in aproximal direction. A space is left between the inside wall of theprotector 3 and the outside wall of the plug 2 at least in a regionaxially located on the proximal side with respect to the frangibleportion 15. In the embodiment shown in FIG. 2b, a space is left betweenthe protector 3 and the mount segment of the plug 2, and the protector 3is in tight engagement with the closing segment of the plug 2. The spacebetween the inside wall of the protector 3 and the outside wall of theplug 2 bridging over the frangible portion 15 is effective infacilitating separation of the plug 2 by tearing it off.

The fourth opening 7 is closed with the plug 2 covered with theprotector 3 when the corresponding branch is not in use. When it isdesired to connect another member to the fourth opening 7, the plug 2 isremoved from the opening by tearing or twisting off the plug 2 at thefrangible portion 15. The fourth opening-defining branch with its flowpath open is now ready for connection to another member.

The frangible portion 15 may be formed at any location between the openend 11 and the closed end 12 of the plug. Preferably, the frangibleportion 15 is provided in the outside wall of the second or larger innerdiameter wall portion 14 of the mount segment of the plug 2. Location ofthe frangible portion 15 in the second wall portion 14 means that thefrangible portion 15 is located radially outside the space 16 betweenthe plug 2 and the branch 7. Then it is very easy to tear off the plug 2by twisting even though the plug is made of a relatively flexiblematerial.

The engagement between the plug 2 and the protector 3 is notparticularly limited as long as it ensures clipping-off of the plug bygrasping the protector 3 with fingers and turning it with the plug 2 soas to tear off the plug without any sliding motion between the protectorand the plug.

In general, medical tubings are made of polycarbonate and flexible vinylchloride resin. When a plug is secured to such a tube, it is desired notto use an adhesive at the connection between the plug and the tube inorder to avoid contamination to fluid to be passed therethrough,typically blood. If a tube and a plug are made of similar types ofmaterial, a blocking bond can be achieved between them by utilizing theheat applied for autoclave sterilization. Since the plug is formed of arelatively flexible material such as polyvinyl chloride resin, it isdifficult to tear off the plug with a click by twisting because the plugas a whole is softly twisted. The protector 3 is preferably made of arelatively rigid material in order to facilitate breakage of the plug 2.A choice of the material of the protector 3 is made such that theprotector may not be bonded to the branch and the plug through blockingunder the influence of the heat applied during autoclave sterilization.A typical example of the relatively rigid material is a polypropyleneresin. A preferred combination of materials meeting the aboverequirement is a combination of polycarbonate for the branch 7 ortubular body, polyvinyl chloride for the plug 2 and polypropylene forthe protector 3. Another preferred combination of materials for thetubular body, plug and protector will occur to those skilled in the artin light of the above teachings.

Also, in the present invention, a space 16 may be provided between aninner wall portion of the plug 2 and a reduced diameter portion 9 of theopening 7. As illustrated in FIG. 5, on the reduced diameter portion 9of the fourth opening 7 in place of on an inner wall portion 17 of theplug 2 may be provided a second stepped down or smaller diameter portion18 to make a space 18 therebetween.

OPERATION

The operation of the four-way branch tube having a plug mounted on onebranch as shown in FIG. 1 is described by referring to a system forplasmapheresis therapy having the branch tube incorproated therein.

As shown in FIG. 4a, the plasmapheresis system includes four sections oftubing connected to the four-way branch tube 1. A first section oftubing extends from a puncture needle 23 placed in the vein of a donor27 to the first opening 4 of the branch tube for the purpose of bloodcollection and has a hemostat 28 thereon. A second section of tubingextends from the second opening 5 of the branch tube to a first bloodbag 24a and has a hemostat 26 thereon. A third section of tubing extendsfrom the third opening 6 of the branch tube to a second blood bag 24bvia a closure member in the form of a click tip 8. A fourth section oftubing extends from the fourth opening 7 of the branch tube to a Y set20. The fourth section of tubing is a trunk line of the Y set whichincludes a first inlet line extending to a physiological saline bottle22 through a clamp 21a and a second inlet line 30 having a clamp 21b.This is an outline of the system, and all the lines are not connected atthe same time. Connection will become apparent from the followingdescription of operation.

While clamps 21a, 21b and 21c on the lines associated with the Y set 20are closed, a needle connected to the line with clamp 21a is puncturedinto the saline bottle 22. Then the clamp 21a is opened and the clamp21b is released to fill the Y set with saline. The clamp 21a is againclosed.

During this operation, the plug 2 on the branch 7 of the four-way branchtube is kept normal or unbroken and covered with the protector 3. Thereis no possibility that the plug is accidentally ruptured to allowcontamination of the opening 7 of the branch during manufacture andsetting of the branch tube 1. The first opening 4 of the branch tube 1is in fluid communication with the needle 23, and the second opening 5in fluid communication with the first blood bag 24a. The third opening 6is connected to the second blood bag 24b although the click tip 8 isalso kept normal or unbroken so that the flow path to the second bloodbag 24b is closed.

The next step is to connect a connector at the free end of the Y settrunk to the branch (7) of the branch tube. The hemostat 26 is fastenedon the second section of tubing connected to the first blood bag 24a inorder to prevent reverse flow of medical liquid in the first blood bag24a. Then the plug 2 is torn off at the frangible portion 15 to open theassociated branch (7) by manually holding and twisting the protector 3.According to the present invention, the plug 2 is made of materialhaving a Shore A hardness of 68 to 76 and the tubular body 1 is made ofa relatively rigid material such as polycarbonate. The first wallportion 3 of the plug is fixedly secured to the tubular body 1. Sincethe tubular body assists in the first wall portion of the plug servingas a rigid support for the plug, a bending force applied to the plug byfingers concentrates at the frangible portion 15. Thus the plug can bereadily ruptured at the frangible portion 15 even though the plug ismade of material having a relatively low degree of hardness. Inaddition, the fact that the plug is made of a relatively flexiblematerial provides the advantage that the plug is resistant againstrupture by an accidental external force. After rupture of the plug, thefourth opening 7 is protruded and exposed without damage. Then theopening is easy to connect another member thereto and free ofcontamination. Easier connection is expected when the fourth opening 7has the Luer taper 7a or an axially outwardly divergent bore.

Further, in the embodiment wherein the plug 2 is received in theprotector 3 of rigid material, the protector in tight engagement overthe plug 2 prevents deformation of the plug and assists in tearing offthe plug at the frangible portion when the protector 3 is gripped andtwisted.

The next step is to collect blood from the donor 27. The first sectionof tubing is fastened by the hemostat 28 at a location near the needle23. The puncture needle is inserted into the vein of the donor 27. Afterentry of blood into the blood collecting tube is observed, the hemostats28 and 26 are taken off to communicate an open continuous flow path tothe first blood bag 24a.

Since the flow path to the second blood bag 24b is closed by the clicktip 8 at this point, blood flows under gravity from the needle 23 to thefirst blood bag 24a. Blood collection is continued until the first bloodbag 24a is filled with a predetermined volume of blood. Then the sectionof tubing to the first blood bag 24a is sealed with a tube sealer or apair of aluminum rings (not shown) and cut therebetween to separate thefirst blood bag 24a.

The whole blood in the first blood bag now removed is centrifugallyseparated into cell and plasma components. During the step, saline istransfused dropwise from the bottle 22 to the donor through the Y set20, the branch (7) with the plug broken, and the needle 23 as shown inFIG. 4b.

The cells thus separated are return transfused to the donor 27. Moreparticularly, an outlet 29 of the first blood bag 24a is connected tothe second inlet tube 30 of the Y set 20. Then the cells are returnedalong with saline to the donor 27 through the Y set 20, the four-waybranch tube 1, and the needle 23.

At the end of return transfusion, the branch tube 1 is held in one hand,and the click tip 8 is manually torn off to open the flow path to thesecond blood bag 24b. Blood is again collected from the donor 27 to thesecond blood bag 24b through the needle 23 which has been placed in thevein of the donor. Likewise the first blood bag 24a, the blood collectedin the second blood bag 24b is centrifugally separated and transfusedback to the donor.

INDUSTRIAL UTILITY OF THE PRESENT INVENTION

In the tube assembly of the present invention, an attachment portion ofa plug of a relatively flexible material having a Shore A hardness of 68to 76 is fixedly secured to a relatively rigid tubular body. Theconnection between the plug and the tubular body is improved in gastightness and intimate contact so that the plug is firmly bonded to thetubular body. Then the plug maintains the ability of being ready to beruptured when the associated tubular body is on use. The risk of theplug being accidentally ruptured by an external force when the tubularbody is not in use is minimized. Thus, contamination of the tubular bodyis prevented when it is not in use.

I claim:
 1. A tube assembly comprising:a tubular body of a relativelyrigid material having at least two open ends, a plug of a materialhaving a Shore A hardness of from 68 to 76 mounted on one open end ofsaid tubular body, said plug including(a) a hollow mount segment havingan open end, a portion of the mount segment extending from its open endbeing fixedly secured to the one open end of said tubular body, (b) aclosing segment axially connected to the mount segment, (c) a frangibleportion located axially outside the secure portion whereby said plug isbreakable at the frangible portion and removable from the one open endof the tubular body; and (d) a protector fitted over the plug.